To produce the upheaval in the United States that changed and modernized the domain of higher education from the mid of 1860's to the mid of 1800's, three primary causes interacted. The emergence of a half dozen leaders in education provided the personal force that was needed. Moreover, an outcry for a fresher, more practical, and more advanced kind of instruction arose among the alumni and friends of nearly all of the old colleges and grew into a movement that overrode all conservative opposition. The aggressive 'Young Yale' movement appeared, demanding partial alumni control, a more liberal spirit, and a broader course of study. The graduates of Harvard College simultaneously rallied to relieve the college's poverty and demand new enterprise. Education was pushing toward higher standards in the East by throwing off church leadership everywhere, and in the West by finding a wider range of studies and a new sense of public duty. The old-style. classical education received its most crushing blow in the citadel of Harvard College, where Dr. Charles Eliot, a young captain of thirty -- five, son of a former treasure of Harvard, led the progressive forces. Five revolutionary advances were made during the first years of Dr. Eliot's administration. They were the elevation and amplification of entrance requirements, the enlargement of the curriculum and the development of the elective system, the recognition of graduate study in the liberal arts, the raising of professional training in law, medicine, and the fostering of greater maturity in student life. Standards of admission were sharply advanced in 1872～1873 and 1876～1877. By the appointment of a dean to take charge of student affairs, and a wise handling of discipline, the undergraduates were led to regard themselves more as young gentlemen and less as young animals. One new course of study after another was opened up: science, music, the history of the fine arts, advanced Spanish, political economy, physics, classical philology, and international law. Which of the following is the author's main purpose in writing the passage?